Automobiles are transported in volume on auto rack train cars. The racks usually consist of stacked long beds that support the automobiles and vertical bars that interconnect the beds. Problems were encountered with these racks since they left the automobiles exposed. Vandals threw rocks through the gaps between the bars. Also, rocks could come up from the road and strike the automobiles. This rock damage could be repaired, but it is quite expensive. Additionally, consumers are notoriously picky about the purchase of a new automobile and do not want to purchase an automobile that has already had some surface damage, regardless of the amount.
To correct these problems, galvanized steel panels are placed between the bars of the train car to block access to the automobiles. The beds, the bars and the brackets that support the side panels are made from metals other than galvanized steel, often, steel or aluminum. Problems arise at the contact points between the galvanized steel panels and the other members. The galvanized panels rust near the contact points due to the contact with the different metals and crack. Since the panels are perforated, a small crack can open a relatively large hole and the purpose of the panels is defeated since there is again access to the car. The rust forms localized weakened spots that cause the panels to bend. This has been a major problem in the automobile industry and has been commented on in the literature. In fact, the mandatory standards adopted by the Association of Americal Railroads, require replacement or repair of any bent or rusted panels and replacement of any cracked or broken panels, that proves very expensive.
The mandatory standards at section 2.3.2 describe mandatory maintenance procedures for the side panels:
2.3.2(d) Replace or repair side screens or panels which are bent inward or outward in excess of 2". PA1 2.3.2(e) Replace any cracked or broken side screens or panels. PA1 2.3.2(f) Enclosed cars equipped with side panels corroded to the extent of loose or flaking rust must be recoated or replaced.